Synthetic pesticide, which account for 70% of world pesticide market, dominates the global market of pest control products. Although synthetic pesticides have improved significantly in recent years on their chemical, environmental and toxicological properties, they continue to pose severe risks of harms to environment and human health due to their persistence and negative effects to non-target organisms. Synthetic pesticides unselectively attack nervous system components that are same in insects and vertebrates. Moreover, the extensive use of these synthetic materials creates tolerance and resistance in more and more pest insects, leading to continuously increase in the dosage of use and increased burden to the environment.
Terpens and terpenoids are important chemical compounds widely exist in plants, which have been found to exhibit insecticidal activities, providing resistance against phytophagous insect damage. For example, terpens and terpenoids exist typically in conifers, Rutaceae, Umbelliferae, Myrtaceae and Labiatae, Asteraceae, Lauraceae, Santalaceae, etc. They also exist in fungus. For example, sirenin can be extracted from Allomyces arbuscula, which resembles a lure to male insects. Terpens and terpenoids are also comprised of pheromones that are emitted from insect osmeterium. Terpenes and terpenoids are characterized by chemical structures of five-carbon isoprene units assembled and/or modified in various ways to form polymer chains or rings, which can be described as (C5H8)n.
The mechanism of the toxic activities of terpenes and terpenoids is under research, although it is hypothesized that they act as allomones or they mimic insect pheromones representing semichemical communications between insect and plant. They are found to deliver in a vapor phase through penetration to target tissues via the respiration system of insects, which can result in antifeedant, repel, allure, growth inhibition, larvacidal, neuron toxication, etc.
Most terpenes and terpenoids that exhibit insecticidal activities are of the following three types: monoterpenes (C5H8)2, sesquiterpenes (C5H8)3 and diterpenoids (C5H8)4.
Although some terpenes and terpenoids are main components of certain essential oils, not all of them are found in essential oils. Therefore, the type of essential oil should not be used to define different types of terpenes or terpenoids. Even for those terpenes and terpenoids that exist in essential oils, the same type of essential oil from different origins or different extraction methods can have different contents within. It is unpredictable based on an essential oil whether it contains a specific terpene or terpenoid and its abundance in the essential oil.
Several applications have been documented involving different types of essential oils or their blends in the purpose of killing or repelling insect pests. U.S. Pat. Nos. 6,114,384; 6,004,569; 6,342,536; 6,376,556 and 6,531,163 relate to a different type of chemicals that are characterized by a 6-carbon ring system which are not of terpenes or terpenoids.
U.S. Pat. No. 6,399,113 describes a lawn pesticide using extracts from cypress mixed with surfactant. However, since the cypress extracts usually contains more than 50 different phyto-chemical compounds and the application doesn't specify which chemical is the active ingredient, there is no way to define its insecticidal property quantitatively or its insecticidal mechanism.
US Patent Application 20030060379A1 describes an insecticidal soap, asserted to be an environmentally friendly pesticide. The disclosure compositions involve all commercially available botanical essential oils without specifying any specific compounds as active ingredients.
There continue to be an urgent need for environmental friendly pesticide compounds, formulations, methods of preparation and methods of using the same.